Cargo in tractor-trailers is frequently unloaded by backing the trailer up against a loading dock. A forklift is then used to transport the product from inside the trailer to the loading dock and storage area. This requires the forklift to enter the trailer repeatedly. It is possible, for various reasons, for the trailer to move away from the loading dock while the forklift and forklift driver are in the trailer. Due to noise and vibration caused by the forklift, this may not be apparent. If the forklift driver than backs out of the trailer, which has moved away from the loading dock, the forklift will fall several feet, which can cause severe injury or death.
There are various alarm systems that can be used to warn individuals if a trailer is inadvertently pulled away from a loading dock. Such systems generally employ an alarm that is located on the loading dock. Such systems are problematic because they require that the system be properly attached to the truck. A forklift driver, once inside the trailer, has no way of knowing or verifying that the alarm system has been properly attached to the trailer. Further, even if the device is properly attached, an alarm outside the trailer may not be heard by the forklift operator. The inside of the trailer reverberates with the sound of the forklift, and, thus, can drown out the sound of an alarm that is located outside the trailer.